knocking at idle when in gear and return line question - PeachParts Mercedes-Benz Forum

networkboy · #1 08-11-2006, 05:30 PM

My "new" car has developed a knocking when in gear at a full stop. I've not been able to tell if it is coming from the engine its self or from something banging from the roughish idle. It sounds like it's coming from the drivers side of the engine compartment, but since it only happens in gear and I don't trust the parking break that much I haven't had an oppourtunity to look under the hood while it's happening. Would a fairly dirty fuel filter cause missing and such like this?

Suggestions?

Also, nobody local carries Viton hoses for the injector return lines. is there an on-line supplier? And, is it really as easy a repair as it looks? Pop off the old and slide on the new?

'83 W123 617.95, 234K miles.

thanks,
-nB

winmutt · #2 08-11-2006, 05:33 PM

Quote:

Originally Posted by networkboy

My "new" car has developed a knocking when in gear at a full stop. I've not been able to tell if it is coming from the engine its self or from something banging from the roughish idle. It sounds like it's coming from the drivers side of the engine compartment, but since it only happens in gear and I don't trust the parking break that much I haven't had an oppourtunity to look under the hood while it's happening. Would a fairly dirty fuel filter cause missing and such like this?

Suggestions?

Also, nobody local carries Viton hoses for the injector return lines. is there an on-line supplier? And, is it really as easy a repair as it looks? Pop off the old and slide on the new?

'83 W123 617.95, 234K miles.

thanks,
-nB

I have no clue why anyone uses the viton lines. Just get the ones from DG or MB dealer. Most newer lines are resilient enough and ALL of them need to be replaced every few years.

If you have air in the line it can cause a very rough idle. Dirty filters would run rough as well. Always carry extras on hand

networkboy · #3 08-11-2006, 05:50 PM

The Viton is what I've been told to get if I want to do the WVO or bio-diesel "thing". I figured that I should do it right the first time...
If you think the rubber ones are good enough then cool I guess.

As to the fuel lines, there is a small bubble in the pre filter and the rest is black.

The car sat for 1.5 years prior to my acqusistion and seing as this issue didn't start till I added a bottle of additive and a tank of fuel I'm guessing the filters are clogged up. I'm thinking the next round of filters will be fairly clogged as well so I might as well use the dented one as it will only be on there for one or two tanks worth of fuel as I clean the system out. It's that or wait for the round trip for a new filter.

Also, I managed to stall the car (in a parking lot, shortly after starting it, engine still hot), simply by turning the wheel agressively while barely rolling forward.

So my plan:
replace filters and purge system. Run some cleaning additive through the system (two tanks or so), replace filters again, ensure good additive each tank thereafter.
-nB

BodhiBenz1987 · #4 08-11-2006, 06:13 PM

Quote:

Originally Posted by networkboy

Also, nobody local carries Viton hoses for the injector return lines. is there an on-line supplier? And, is it really as easy a repair as it looks? Pop off the old and slide on the new?

-nB

I just get them from the MB dealership. They really are not that expensive, so I don't think it's worth it to buy anything cheaper ... I know I can trust the MB bits. And, yes, it really is as easy as it looks. Proof: I've done it. The only PITA is doing the one under the air intake on the OM 603, but as far as I know the 617 has no such problem. Don't be stupid like me and try to do it right after you've shut off the engine, when the fuel is still sitting in the lines ...

VegiBenz · #5 08-11-2006, 06:21 PM

Is your return hose a cigar hose? If not, it can transmit the injection pump pulses to the return metal line and cause it to knock against the body. My old 84 300D did that. The cigar hose acts as sorta an accumulator. If you have a cigar hose there then maybe it is just your rough idle physically transmitting the motion of the engine to the metal line. Eric.

networkboy · #6 08-11-2006, 06:46 PM

Cigar hose.
I've got a pad to land the car on this weekend, and the return lines are on order (from here). So, we'll see how it goes. Hope the filter change does it.
Cheers,
-nB

dieseldiehard · #7 08-11-2006, 06:47 PM

Quote:

Originally Posted by winmutt

I have no clue why anyone uses the viton lines. Just get the ones from DG or MB dealer. Most newer lines are resilient enough and ALL of them need to be replaced every few years.

If you have air in the line it can cause a very rough idle. Dirty filters would run rough as well. Always carry extras on hand

I use and have provided Viton return hose to others who, like me, want a return hose that will not start weeping diesel fuel in a year or 18 monts or so.

Note that this applies only to the OM603 which doesn't need valve adjustments of course. For 617 engines I stick with the regular OE return hose. By the time they start weeping fuel its time for a valve lash and they get changed out.

Viton is great stuff for Bio users also that experience premature failure of the OE hoses where the rubber compound seems to get soft from Bio fuel. Viton is great stuff!

dieseldiehard · #8 08-11-2006, 06:53 PM

Quote:

Originally Posted by BodhiBenz1987

I just get them from the MB dealership. They really are not that expensive, so I don't think it's worth it to buy anything cheaper ... I know I can trust the MB bits. And, yes, it really is as easy as it looks. Proof: I've done it. The only PITA is doing the one under the air intake on the OM 603, but as far as I know the 617 has no such problem. Don't be stupid like me and try to do it right after you've shut off the engine, when the fuel is still sitting in the lines ...

Not stupid that, anybody can make a mistake. But getting a face full of hot diesel is something I've experienced

At least let it cool down!

I have found that on the 603 engines if you remove the fuel filler cap on cars that have a positive pressure in the fuel tank, you will not get a pissing stream of fuel out of the return lines, instead only a few drops to clean up.

Palangi · #9 08-12-2006, 12:32 AM

Air cleaner mounts broken?

networkboy · #10 08-12-2006, 12:42 AM

Quote:

Originally Posted by Palangi

Air cleaner mounts broken?

I'll check tommorow. Anything obvious to look for? like pull on the housing and if it comes loose that's it?

I'm learning a whole new world of engine work on this car. First diesel I've ever touched

all the noises are different than any of my gas burners MB or otherwise.
-nB

Palangi · #11 08-12-2006, 12:55 AM

Just check if it moves left-right far enough to bank into the valve cover. It is held by 3 rubber mounts which break in about 20 years.

P.E.Haiges · #12 08-12-2006, 05:08 AM

Net,

Black fuel in filter usually means fungus is in your fuel system. Only cure is adding a fungacide.

If your engine has full power underload, there is nothing wrong with your filters.

Many times, knocking at idle is caused by injectors. Loosen the nut on the top of your injectors, one at a time, and see if knocking goes away. If it does, switch 2 injectors and notice if the knocking moves with the suspected injector. If it does, you need another injector or yours rebuilt.

P E H

networkboy · #13 08-12-2006, 04:42 PM

Update:
Fuel its self was looking ok, but the filter body had a charcoal grey film in it.
> Changed fuel filters
> Removed air filter boy was it nasty! Last changed in 1999 according to what was written on it in sharpie! (idled the car without the filter for a few minutes, obviously no driving this way).
> Chocked wheels, got a chance to listen to the engine. It is missing, gets worse as the engine heats up. (this after air filter removed and fuel filters changed).
> Oil looks like India Ink it is *that* black. I'd venture that while diesels may be different that gas burners, the oil still shouldn't be that bad.
> Noises are evolving as the car is run, (sounding worse).
> Power below 2K RPM is non existant, power is fading fast compared to the first test drive above 2K RPM as well.

On order:
Air and oil filters, spare fuel filters, return line material (leaking like they might as well not be there).

Suggestions?
Sounds like it is the injectors as P E H said, so that's next on the list.

Cheers and tons of thanks,
-nB

networkboy · #14 08-13-2006, 12:54 AM

Someone else mentioned that I could pull the return line from the fuel filter and using a syringe, inject some injector cleaner into the system while the engine is idling and see if that does the trick...

Any thoughts?
-nB

dieseldiehard · #15 08-13-2006, 12:58 AM

Quote:

Originally Posted by networkboy

Update:
Fuel its self was looking ok, but the filter body had a charcoal grey film in it.
> Changed fuel filters
> Removed air filter boy was it nasty! Last changed in 1999 according to what was written on it in sharpie! (idled the car without the filter for a few minutes, obviously no driving this way).
> Chocked wheels, got a chance to listen to the engine. It is missing, gets worse as the engine heats up. (this after air filter removed and fuel filters changed).
> Oil looks like India Ink it is *that* black. I'd venture that while diesels may be different that gas burners, the oil still shouldn't be that bad.
> Noises are evolving as the car is run, (sounding worse).
> Power below 2K RPM is non existant, power is fading fast compared to the first test drive above 2K RPM as well.

On order:
Air and oil filters, spare fuel filters, return line material (leaking like they might as well not be there).

Suggestions?
Sounds like it is the injectors as P E H said, so that's next on the list.

Cheers and tons of thanks,
-nB

Diesel engines leave a lot of soot in the oil, its normal to see it get thick and black even just a few hundred miles after an oil change
What are the worsening noises you refer to, Engine related?